Number 2 fuel oil, the conventional fuel for automotive diesel engines, has a pour point at about 20.degree. F. Below that temperature the oil congeals, and if the oil temperature falls substantially below the pour point the oil will not flow satisfactorily from the fuel tank through the vehicle fuel lines. Thus, at oil temperatures about zero degrees or below, diesel automotive vehicles become difficult or impossible to start. Number 2 fuel oil can be winterized by blending with Number 1 fuel oil (pour point minus 16.degree. F.) Once the engine is started it generates enough heat at ambient temperatures some way below the fuel pour point to keep its fuel flowing, but when ambient temperature reaches 15.degree. or 20.degree. below zero F. normal fuel flow cannot be maintained.